[Functional acute kidney failure]

Prerenal acute renal failure is defined as a reduction in the glomerular filtration rate due to a primary disturbance in renal hemodynamics in the absence of any structural kidney damage. In case of moderate hypotension or hypovolemia, a number of adaptative systemic and intrarenal responses preserve renal perfusion and filtration rates, particularly by inducing a marked reduction in preglomerular arteriolar resistance and an increase in postglomerular resistance. However, these mechanisms are inherently limited. In the presence of advanced circulatory failure or iatrogenic pharmacologic interventions compromising these renal defense mechanisms, prerenal failure becomes evident. Therefore, prerenal failure may occur during acute hemodynamic disturbances due to hypovolemia or systemic vasodilatation, in severe cardiac failure, in cirrhosis with ascites, and in certain clinical situations following administration of nonsteroidal antiinflammatory agents or angiotensin converting enzyme inhibitors. The treatment depends on the underlying cause.